The most memorable day of Patrick Reed's golfing life was overshadowed by the latest glaring signs of the physical fallibility of Tiger Woods. The world No1 lasted beyond 13 Sunday holes this time, despite frequent indications he would not even manage that.

Reed's nerveless display makes him the youngest winner of the WGC-Cadillac Championship at 23, beating Woods' record in 1999 by 96 days. When Woods created it, he was in a completely different condition from now; his back spasm problems are obvious and a major issue. The fact that a historically guarded Woods admits as much is notable in itself.

"It's over. It's finally done, which is good," said Woods after signing for 78. "If I feel good, I can actually make a pretty decent swing. You saw that on Saturday. I actually can make some good swings and shoot a good score but if I'm feeling like this, it's a little tough."

Woods started day four at Doral three shots off the lead. Yet his injury is triggering inconsistency; after dropping shots on the 3rd and 4th he was suddenly seven adrift of Reed. By the time he had played a bunker shot from an awkward lie on the 6th Woods was holding his back.

It proved a recurring theme. By the 10th the 38-year-old toiled to pick up his tee peg. Woods even had clear struggles standing for any length of time over putts.

"If it flares up, it flares up," Woods said. "It's just a matter of keeping it calm and we had a quick turnaround here from last week. It would be nice to have a week off where I can shut it down and get some treatment.

"The deeper the flexion, the worse it felt. But as I set up to the ball, it is already there. I'll get some more treatment and we'll assess it as time goes on."

Time, however, is not on Woods' side with the first major of the season only a month away. He is scheduled to play again at Bay Hill, starting on Thursday week, but there must be question marks over that.

At four under par Reed won by one from Bubba Watson and Jamie Donaldson. The latter's case for a place in the European Ryder Cup team in September is seriously strong; Donaldson could have applied even more pressure to Reed but failed to get up and down from a greenside bunker on the 18th. Reed, with a two-shot lead playing that hole, was entitled to play safe and accept a bogey five, which was duly the case.

"I've not played great in America, in the events I've played in," admitted Donaldson, a Welshman. "So it's nice to come here and have a great week on what is a very tough course."

This marks Reed's second win of 2014. He lifted the WGC-Cadillac trophy aloft after his first appearance in the tournament. "To come out in a field like this and to hold on like that, I feel I've proven myself," Reed said. It was fair comment.

Donaldson was not the only prominent European by close of play. Stephen Gallacher had an excellent fourth-round 69 to earn a tie for sixth at one over par. Gallacher's participation in the Masters is now confirmed but he dismissed the notion that he would consider playing full-time in the United States.

"My kids are in school and they are happy," said the Scot. "I will just play here the weeks that I can, before majors and stuff like that. This was only my second time playing a WGC event so it was a great experience for me."

Miguel Ángel Jiménez was on the same score as Gallacher playing the 72nd hole but watched his second shot bounce into the greenside water hazard. This induced an uncommon flash of temper from the Spaniard, who threw his fairway wood away in disgust before holing out for double bogey.

Rory McIlroy's love-hate relationship with this revamped course continued with a closing round of 74, which left him at plus five overall and tied 25th.

"It was more frustrating than anything else," McIlroy said. "I hit 14 greens. I felt like I struck the ball well for the most part, it was just on the greens that I didn't get anything going. Any time I missed the greens, I didn't really get up and down.

"It's a frustrating course because you feel you should be doing so much better. It just doesn't allow you to. You have to be so precise just to get the ball close on some of these greens, with these pin positions. I got to the turn on even par and thought I should be three or four under. I feel like I played a lot better than what the finish and the score suggests."

McIlroy headed immediately for California to join his fiancée, the tennis player Caroline Wozniacki, who will compete in the BNP-Paribas Open at Indian Wells this week.